Electric arc lamp



June 29, 1937- G. E. INMAN x-:T Al. v 2,085,531

ELECTRIC ARC LAMP Filed- Jan. 5, 1934 2 sheets-sheet 1 3 INI/ENTDAE GE 7A 5E E' ZNMN EUEEAELE was f 'BY THEIR .AIT Taalva- :Y

Patented v June 29, 1937 UNITED srlif'rias-y 2,085,531 g ELECTRIC Anc LAMP GeorgeE. Inman, Cleveland Heights, v and Eugene Lemmers, Cleveland, Ohio, asslgnors to General Electric Company, a corporation of New York Application January 3, 1934, serial No. 705.048 y rclaims., (ci. 116-122,)

vOur invention relates to electric arc lamps of the type comprising refractory metal electrodes sealed in a transparent or translucent bulb or other container. Our invention may be applied to arc lamps of the type disclosed in our pending application Serial No. 618,894, filed June 23, 1932. The lamp disclosed in our pending application consists of a bulb filled with a readily ionizable gas, such as argon or neon, andcontains a pair of special electrodes and a resistance heater. The Vsaid heater comprises a coil of refractory wire, connected in series with the arc gap and encased in a refractory and insulating tube which extends in heat conductive relation to a body of a vaporizable metallic substance, such as mercury or sodium, in the bulb. The electrodes each comprise a surface coated with a thermionically active material used in combination with a refractory terminal. However, the present invention contemplates the use of electrodes comprising a compact mass of refractory metal impregnated or alloyed with a thermionically active material thus dispensing, if desired, with the` refractory terminal, which was used in the electrodes of the said pending application to carry the arc discharge in order to protect the coated surface from disintegration. The said coated surfaces aid in thestarting of the arc, wherein a glow or diffuse discharge takes place around the electrodes which concentrates, as the temperature and pressure build up, to an arc, which strikes across the refractory terminals, said terminals being directly in the arc path and closer together than said coated surfaces. The heat from the discharge and the heat radiated from the refractory terminals maintain the coated surfaces in an active condition. 'I'he said coated surfaces therefore serve the double purpose of facilitating starting and aiding in the maintenance of the high pres- 40 sure arc. l

Oneof the objects of our invention isto provide an arc lamp which will be an efficient source of visible and/or ultra-violet rays and which will operate directly from a line carrying the ordinary commercial voltage (approximately 110 volts) without the use `of a transformer or other externai equipment. Another object is the elimination of a starting electrode by providing novel forms of electrodes or the provision of a novel form of starting electrode to be used with the electrodesdescribed above. insure more positive starting and to maintain more of the active electrode surfaces at the proper temperature. Still another object is the possible elimination of the starting gas in the bulb.

Other objects are to II According to the present invention the abovementioned objects are attained by providing either one or both main electrodes with heater filaments disposed adjacent to the coated surface. In the above-mentioned type of lamp, starting of the arc was sometimes delayed because of a deposit of vaporizable metal on the coated surface. 'I'his objectionis avoided by the use of the'heating elements which vaporize the said vaporizable metal from the coated surfaces and thereby permit access to the active surfaces. In a modified form, the heater element may be provided in an auxiliary starting electrode. Either of these constructions provides more positive starting and more uniform and more nearly correct operating temperature of the active surfaces of the electrodes with a lamp of ordinary design.

Further features and advantages ofour invention will appear` from the following detailed description of species thereof and from the drawings.

In the drawings, Fig. l is an elevation of a form of lamp comprising our invention; Fig. 2 is an elevation at right angles to the view in Fig. 1; Fig. 3 is an elevation, partly in section, of a form of electrode used in our` lamp; Fig. 4 is a diagrammatic view of a circuit adaptable for `the lamp; Fig. 5 is an elevation, in section, of a modified form'of electrode; Fig. 6 is a perspective view of 3 another modified form'of electrode; Figs. 'l and 8 are elevations, at right angles to each other, of la modified form of lamp employing an auxiliary starting electrode; Fig. 9 is an elevation, in

section, of a form of starting electrode; Fig. 10 3 -illustrated in detail in Fig. 3. Each of the elec-' trodes I2 comprises a metal memberl such `as a tube I3 (Fig. 3) preferably of nickel. 'I'he said tube I3 is mounted at one end on an insulating collar I4 which is mounted on a conductor `I5 which carries a refractory metal terminal I6 at its ond which is located just beyond the edge of said tubel3. Instead of the tube I3 a disc or cup, or a compact mass of material having a surface which will easily emit electrons, may also be used. The said tube I3 has a coating I1 of a thermionically active compound, preferably an alkaline earth metal compound such as barium oxide,l on the surface thereof. In the form of 5 electrode shown in Fig. 3, the coating I1 is impregnated in the turns of a helically wound coil I8 disposed on the inner surface of said tube '13. The said tube I3 is electrically connected to the conductor I5 by conductive straps I9. An

lo insulating tube is disposed around the tube f I3 and a heating element 2| is wound around said tube 20 and is covered with insulating cement 22. The heater 2I may be incorporated in only one of the electrodes, either upper or lower, if de- 15 sired. 'I'he tube I3 may also be made of tungsten, molybdenum or Konel metal, and in addition to barium oxide, the coating thereon may comprise strontium or calcium oxides or combinations thereof. t0 The conductor I5 of upper electrode I2 is connected to a leading-in wire 23 which is sealed in the press portion 24 of a stem tube 25. The conductor I5 of lower electrode I 2r is mounted on a cross support wire 26 which is mounted on ..ooutwardly extending portions 21 and 28 of a wire 28 which is coiled about a refractory insulating tube 30. The end portion 21 of the wire 23 is connected to a conductor 28 which is covered with an insulating tube 3I and an insulating cov- 30 ering 3I and extends through the stem press 24.

A heater comprising a coil 32, preferably of tungstenvor nichrome, extends through the tube 30 and is mounted on the inner end of conductor 33 and leading-in wire 34 which extend through 35 the stem press 24. The said tube 30 is preferably of beryllium oxide and is formed into substantially a U shape, the legs of the U extending along the gap between the electrodes and the `bent portion passing between the lower electrode o I2 and the end of the bulb II. 'I'he said bent portion of tube 30 passes adjacent to, or preferably through, a tool of vaporizable metal such as mercury 35 located in the bulb II. 'I'he inner end of a conductor 36 which is covered by an insulating tube 31 is embedded in an insulating bead 38 which is mounted on the outwardly extending portion 28 of wire 29. The opposite end of lead wire 31 is connected to a support wire 39 one end of which is embedded in the stem press 50 24. One end of each of the heating elements 2I of electrodes I2 is connected to the tubes I3 while the opposite ends are each connected to conductor 36.

The tube 30 is heated to luminescence by the 5:, heater 32 thus increasing the vaporization of mercury from the pool 35 and greatly increasing the concentration of mercury vapor in the region' of the arc which is located directly over the heated pool. 'I'he ultra-violet efficiency inu) creases rapidly with increasing mercury vapor concentration. Theinner ends of conductor 33 and leading-in wire 34 are disposed in short glass tubesr 48and 4I extending from the stem press 24 and insulating tubes 42-43 are disposed about the said tubes 40-4I and the ends ofgtube 30 thereby preventing the formation of an arc at said lead wires. Although beryllium oxide is to be preferredfor the tube 30, other refractory substances may be used such as thoria, alumina m or magnesia.

f Referring to Fig. 4, one circuit for the lamp is from lead wire 23 through conductor I5 of upperv electrode I2, tube I3, through the heating element 2|, conductor 36, heating element 2I of u lower electrode I2, tube Il, conductor I5. conductors 26, 21, 28, and 33, heater 32 and lead wire 34. 'I'he lead wires 23 and 34 are connected to respective terminal elements in the base I0., At the start of the operation of the lamp a glow discharge takes place around the upper and 5 lower electrodes I2. Said discharges increase in size and strength as the temperature and pressure build up within the lamp until an arc discharge is formed which strikes across terminals yI6'since they are closer together than the tubes 10 I3. When the arc is formed the greater amount of current goes through the arc and only a small amount through the heating elements 2|.,

An auxiliary starting point may be provided adjacent the electrodes I2 to insure easier start- 15 ing. The said starting points are provided by wires 43 mounted on conductor 36, the ends of said wires extending adjacent the edges of tubes I3 of said electrodes I2. The said wires 43 thus provide short gaps to the main electrodes so 20 that discharges are formed therebetween which subsequently transfer directly across the main electrodes,|2.

Fig. 5 shows a modiiied form of electrode 44 in which the heater 45 is located inside of the 25 tube 46. The said tube 46 is mounted at one end on insulating collar 41 which is mounted on a conductor 48. The conductor 48 is preferably of tungsten and has a terminal 49 at the end thereof which extends just beyond the edge of 30 tube 46. An insulating tube 50 surrounds the conductor 48 and the heater 45 is wound therearound and has a coating 5I of insulating cement thereon. A thermionically active material 52 is disposed in the turns of a helically wound coil 35 53 which is located in the tube 46. 'I'he tube 46 is connected by conductive straps 54 to the conductor 48 and one end 0f the heater 5I is connected to conductor 48.

Fig. 6 shows another modified electrode com- 40 prising a heater 55' embedded in a hollow cylindrical mass of insulating cement 56 in which is disposed a length of refractory metal screen 51' which is impregnated with a thermionically active material and is rolled into a compact cylin- 45 drical mass. A conductor 58 is electrically connected to the metal mass 51. The outer edge of the said metal mass 51 is able to withstand the effects of the arc discharge while the thermionically active material within the mass con- 50 tinues to emit electrons. An alloy, such as a nickel-barium alloy, may be used instead of the impregnated screen 51. Also a refractory terminal ball, such as the ball I6, may be used in conjunction with this type of electrode. 55

Figs. 7 and 8 show a modified form of lamp employing a heated auxiliary starting electrode. The lamp comprises a base 55 and a bulb 56 which may or may not be filled with a readily ionizable gas such as argon or neon. A pair of 60 combination main electrodes 51 are located in said bulb. The said electrodes each comprise a metal member such as a tube 58 which is mounted at one end on an insulating collar 59. Said collar 58 is mounted on a conductor 60, prefer- 65 ably of tungsten, which has a lterminal 6I at the `end thereof. The tube 58 is connected by conductive straps 62 to conductors 60. A coating 63 of thermionically active material is disposed on the surface of said tube 58, the drawings showing said coating on the inner surface of the tube although it may also be applied to the outer surface. Of course electrodes of the type shown in Fig. 6 may be substituted for electrodes 51.

Conductor 68 of upper electrode 51 is connected 75 the press portion 65 oa stem tube 66.

toa leading-in wire 64 which extends through The lconductor 60 of lower electrode 51 is mounted on` one end of conductor 61 which is coiled about a refractory insulating tube 68. `The opposite end of` conductorw61 is connected to a conductor 69 which has` an insulating tube 10 and an insulating covering 18' thereon and which extends through the stem press 65. -A heater 1| is mountpreferably consists of beryllium oxide, and extends in heat conductive relation to a pool of vaporizable metal 13', said metal being mercury when using the lamp as a source of ultra-violet light. The inner ends of conductor 12 'and lead wire 13 are surrounded by short glass tubes 14-15 which extend from the stem press 65. 'Ihe tubes 14-15 and the ends of tube `68 are covered by insulating tubes 16-11.

Starting electrode 18 is disposed adjacent the upper electrode 51 in the drawings, although it may be placed adjacent the other electrode or between the two main electrodes. The said electrode 18 comprises ya metal tube 19 (Fig. 9) mounted at one end on an insulating collar 88 which is mounted on a conductor 8|. The said tube 19 is electrically connected to said conductor 8| by a strap 8|'. A quantityof thermionically active material 82 is coated on the outer surface of tube 19. An insulating tube 83 is disposed within the tube 19 and a heating element 84 is disposed in said tube 83. j One end of heater 84l is connected to conductor 8l and the other end is connected to a conductor 85. Conductor 8| is mounted on a conductor 86 which extends through the stem press 65 and is connected .through a resistance 81 in the base 55 to conductor 69. Conductor 85extends through stem press 65 and is connected through a resistance 88 to lead wire |54.`

Referring to Fig. 11, the main circuit is from lead wire 13 through heater 1 I, conductor 12, coni trode tube 58. The said discharges increase in size and strength as the temperature and pressure build up within the lampr until an arc discharge is formed which strikes across terminals 6i of the electrodes since they are closer together than the tubes 58. When the arc is formed the resistances 81 and 88 and auxiliary electrode 18 are substantially cut out of the circuit, practically all the current going through the arc.

What we claim as new and desire to secure by Lettters Patent of the United States, is:

l. An'electric lamp of the high pressure concentrated arc type comprising a single glass bulb, a pair of electrodes in said bulb each comprising a metal portion having a coating of a thermionically active material thereon and defining a positive-column-path therebetween a separate concentrated refractory metal terminal body of substantial heat capacity mounted adjacent to, and projecting beyond and spaced from the vend of, said coated metal portion, and a heating element adjacent at least one of said coated metal portions, said electrodes being so disposed that said terminal bodies are closer together than said coated metal portions, a quantity of vaporizable.

metal in said bulb, and a resistance element having a covering of refractory insulating material extending in heat conductive relation to said vaporizable metal.

2. An electric lamp of the high pressure concentrated arc type comprising a single glass bulb, a pair of electrodes in said bulb each comprising a metal portion having a coating of a thermionically active material thereon and defining a positive-column-path therebetween, a separate concentrated refractory metal terminal body of substantial heat capacity mounted adjacent to, and projecting beyond and spaced from the end of, said coated metal portion, and a heating element adjacent at least one of said coated metal portions, said electrodes being so disposed that said terminal bodies `are closer together than said coated metal portions, a' quantity of vaporizable metal in said bulb, and a resistance element in series with the arc gap between said electrodes having a covering of refractory insulating material extending in heat conductive relation to said vaporizable metal.

3. An electric lamp of the high pressure concentrated arc type comprising a single glass bulb,

a pair of electrodes in said bulb each comprising a metal portion having a coating of a thermionically active material thereon, and defining a positive-column-path therebetween, a separate concentrated refractory metal terminal body of lsubstantial heat capacity mounted adjacent to,

and projecting beyond and spaced from the end of, said coated metal portion, and a heating element adjacent each of said coated metal portions, said heating elements being connected in series and said electrodes being so disposed that said terminal bodies are closer together than said coated metal portions, a quantity of vaporizable metal in said bulb, and a resistance element in series with the arc gap between said electrodes having a covering of refractory insulating material extending in heat conductive relation to said vaporizable metal.

4. An enclosed arc device comprising a bulb, refractory metal main electrodes in said bulb, a coating `oi' a thermionically active material on said electrodes, a resistance in series with the arc I gap between said electrodes, and an auxiliary starting electrode in said bulb, said auxiliary electrode comprising a metal portion having a coating of thermionically active material and a heating element adjacent said coated metal portion and electrically connected in multiple with said main electrodes.

5. An enclosed are device comprising a bulb, refractory metal main electrodes in said bulb, a coating of a` thermionically active material on said electrodes, and an auxiliary starting electrode in said bulb, said auxiliary electrode comprising a metal portion having a coating of thermionically active material and a heating element adjacent said coated metal portion and electriv cally connected in multiple with said main electrodes.

6. .An enclosed arc device comprising a bulb, a pair of electrodes in said bulb eachcomprising a metal portion having a coating of a thermionically active material thereon, and a separate concentrated refractory metal terminal body of substantial heat capacity mounted adjacent to, and projecting beyond, said coated metal portion,

said electrodes being so disposed that said terminal bodies are closer together than said coated metal portions, a quantity of vaporizable metal in said bulb, a resistance element having a covering of refractory insulating material extending in heat conductive relation to said vaporizable metal, and an auxiliary electrode in said bulb, said auxiliary electrode comprising a metal portion having a coating of thermionically active material and a heating element adjacent said coated metal portion. v

7. An enclosed arc device comprising a bulb, a quantityof vaporizable metal in said bulb, a pair of spaced refractory metal electrodes in said bulb detlning therebetween a positive-column-path and having a coating of thermionically active material thereon, a ballast resistance heater in said bulb in series with the arc gap between said electrodes. said ballast resistance heater being substantially U-shaped and having a covering oi.'

refractory insulating material thereon, the legs oi' said U extending along the arc gap between said electrodes on opposite sides thereof and the connecting portion of said legs extending in heat conductive relation to said vaporizable metal, and a heating element adjacent at least one of said electrodes, said electrodes being so disposed that the arc gap therebetween extends longitudinally of said bulb and in the path of vapors volatilized from said vaporizable metal. .l

GEORGE E. INMAN. EUGENE LEMMERS. 

